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Commercial Water Reclamation. Presented by: Brian Soderholm Water Control Corporation. Water Reclamation is Not a New Concept!. 1500 year-old, 21 million gallon Basilica Cistern in Istanbul, Turkey. You May Have Major Questions!. How big of a rainwater cistern to use?

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Commercial Water Reclamation

Presented by: Brian Soderholm

Water Control Corporation

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Water Reclamation is Not a New Concept!

1500 year-old, 21 million gallon Basilica Cistern in Istanbul, Turkey.

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You May Have Major Questions!

  • How big of a rainwater cistern to use?

  • What to do with rainwater?

  • What are other sources of reclaimable water?

  • Where can I use graywater?

  • What are the benefits and payback?

  • What about sanitation? Is it safe?

  • How to collect the water?

  • How to store the water?

  • How to best disinfect the water?

  • How to best deliver the water to fixtures?

  • What system options are available in the market?

  • What about code compliance?

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Sizing a Cistern: Educated Guessing

  • 1 ft² roof surface can generate approximately 0.62 gallons of usable water per inch of rainfall.

    • Example: a 15,000 ft² roof in MN could generate approximately 15,000 X 4.34 X 0.62 = 40,362 gallons in an average July.

  • A 40,000 gallon cistern may not be practical in a wetter climate.

    • Only full after spring snow melt or major storm!

    • Fixtures/equipment may not require so much water

    • (in a dry climate, size near 100% and look for other sources)

    • Wetter Climate Rule of Thumb: divide total gallons by avg. peak monthly rainfall events – ex. For MN: 2 or 3 (i.e. 20,000 or 13,ooo gallon cistern) and compare to gal. required.

      • Choose the smaller of the two when sizing cistern.

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Other Potential Sources:

  • Cooling System Condensate:

    • 0.1 gal/ton hour at 70% relative humidity

    • 0.2 gal/ton hour at 80% relative humidity

    • 0.3 gal/ton hour at 90% relative humidity

      • Challenge: low pH, bacteria

  • Cooling Tower Blowdown

    • Challenge: high TDS, chemicals

  • Groundwater

    • Challenge: soil-based minerals

  • Softener/Filter Backwash

    • Challenge: suspended solids and high TDS (depending on type of filter)

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Many Potential Uses:

  • Rainwater can be collected and re-used for:

    • Landscape irrigation

    • Cooling tower/Boiler make-up water

    • Tanker filling/ Backup fire systems

    • Nursery irrigation systems

    • Flushing toilets and urinals

    • Vehicle washes

    • Industrial process

  • Potable water applications not recommended – and probably not legal!

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  • Graywater Reclamation:

    • Graywater = Water from showers, bathroom lavs, clothes washers, (possibly pool backwash).

    • Reclaimed for sub-surface irrigation and (possibly) fixture flushing

      • Toilet/urinal flushing requires disinfection and is only legal/possible without special approval in IPC (and IPC-based) states!

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  • Graywater System Design Considerations:

    • Enough storage for 1 or 2 days’ demand (code dependent).

    • Tank water should turn at least every 3 - 7 days (code dependent).

    • Overflow to sanitary sewer

    • No blackwater! (toilet, kitchen sink, laundry with diaper service, etc.)

    • Occupant # / Graywater discharge estimation tables in UPC and IBC

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Water Reclamation: Many Potential Advantages:

  • Up to 12+ LEED™ points may be available:

    • “Stormwater Design: Quantity/Quality Control (2)”

    • “Water Efficient Landscaping (4)”

    • “Innovative Wastewater Technologies (2)”

    • “Water Use Reduction (4+)”

    • A virtual MUST for LEED™ Gold and Platinum certification!

  • Potential for drastically reduced sewer/water impact fees

  • Reduced water and sewer fees

    • Calculating “payback” requires number crunching!

      • Good systems: $2000 - $200,000

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Potential Pitfalls:

  • Public health risks:

    • Bacteria, algae, pathogens, mold, insects, rodents, (and almost anything else imaginable) seem to find their way into cistern/storage tanks (ask your grandparents!).

      • Graywater is of particular concern.

      • Cooling towers and irrigation systems can diffuse these harmful agents into the air (think Leigionella bacteria!).

      • Toilets, urinals, and other fixtures supplied with reclaimed water can cause internal contact with these agents.

      • = Potential for major liability!

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  • Thoughts on Collection:

    • Consider roof drains with mesh screens if debris on roof will be minimal

    • Pre-filtration is always highly recommended!

    • Water from drain tiles may contain iron or other minerals (extra filtration required)

    • Water from parking lots not recommended:

      • May contain salt, oil, antifreeze, trash, goose feces, etc.

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  • Thoughts on Storage:

    • Polyethylene, fiberglass, corrugated (lined), galvanized steel or concrete tanks (verify compatibility with disinfection method)

    • Buried or located indoors in northern climates

    • Overflow, vent, manhole access, and inlet/outlet tappings required

    • If above-ground, consider black or green color to prevent algae growth

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Disinfection: Which Method to Use?:

  • Chlorination (oxidation):

    • Advantages:

      • Measurable

      • Residual disinfection

    • Disadvantages:

      • Not terribly “green” (LEED®)

      • Chemical handling and storage

      • Not good for landscaping

      • Expensive/ongoing chemical purchase

      • Trihalomethanes (THM’s) and other harmful byproducts!

      • Only ClO2 effective with algae

•Calcium hypochlorite tablets

•Sodium hypochlorite solution

•Chlorine gas

•Chlorine dioxide solution

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Disinfection: Which Method to Use?:

  • Ultraviolet (DNA destruction to prevent replication):

    • Advantages:

      • No chemicals

      • Relatively low cost and maintenance up to 80 GPM systems

    • Disadvantages:

      • No residual disinfection (circulation highly recommended!!!)

      • Ineffective if water is discolored or turbid (UV sensor highly recommended!!!)

      • Not as effective with viruses or cysts

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Disinfection: Which Method to Use?:

  • Ozonation (oxidation using O3):

    • Advantages:

      • No chemicals – generated on demand

      • 2000 times faster than chlorine

      • Back to O2 in approx. 17 minutes

      • Residual disinfection

      • Powerful deodorizer

      • Works in dirty/discolored water

      • Measurable

      • May help with Green Roof discoloration

    • Disadvantages:

      • More $$ and maintenance if under 80 GPM

      • Cistern cannot be vented indoors w/o destructor

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  • Thoughts on Delivery:

    • pH may be an issue! (consider appropriate piping materials!). Ozone/ chlorine also corrosive.

    • Particulate filtration needed prior to delivery (cartridge, bag, basket, or membrane filter)

    • Most states have strict marking requirements (“Non-Potable Water”)

    • Incorporate a fresh-water bypass or make-up if tank goes dry, disinfection goes down, etc.

      • Ensure appropriate backflow prevention! (RPZ assembly or “break tank” with air gap).

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  • So How Are People Doing It?

    • Individual component systems designed in-house (contractor builds)

    • Residential or light commercial “rainwater harvesting kits”

    • Large commercial turnkey systems

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What About The Codes???

  • Code Issues:

    • A lack of clarity and consistency in state codes can lead to confusion, delays, and disapprovals.

      • Public health concerns

      • Confusion at state, engineer, customer and inspector level

    • Current code status:

      • IPC: Rules for graywater only – no rainwater

      • UPC: Rules for graywater and municipally treated wastewater. Rainwater code currently under development

      • Draft codes being developed by ARCSA, IAPMO

      • California Title 22 statutes and USEPA 2004 Guidelines for Water Reuse

  • Plan Review is the norm! The more robust a system, the less likely you are to experience hang-ups at state or inspector level!!!